Method and apparatus for improving the performance of suction powered pool cleaning systems

ABSTRACT

A pool cleaning system including means responsive to the magnitude of negative pressure at the suction inlet of a system pump for controlling pump water flow in order to prevent pump cavitation. Systems in accordance with the invention are configured to pump a high rated volume of water when operating in a filtering mode and to provide a high negative pressure to power a pool cleaner when operating in a cleaning mode.

RELATED INVENTIONS

This application is a continuation of PCT2006/027495 filed 13 Jul. 2006 which claims priority based on U.S. Application 60/705,080 filed 8 Feb. 2005. This application claims priority based on the aforementioned applications.

FIELD OF THE INVENTION

This invention relates generally to a swimming pool cleaning system utilizing an electrically driven pump for powering (1) a pool water filtration system and (2) an automatic pool cleaner; and more particularly to system improvements for preventing pump cavitation and for increasing the negative operating pressure (i.e., suction) available for powering the pool cleaner.

BACKGROUND OF THE INVENTION

Typical pool cleaning systems include an electrically driven pump which draws pool water into its suction inlet and discharges the water from its pressure outlet. The pool water drawn into the pump inlet is most typically captured by a pool skimmer and/or drain. The pool water discharged from the pump outlet is typically passed through a filter (and, optionally, a heater and/or chlorinater) prior to being returned to the pool. A pump appropriately sized for the particular pool installation should produce a flow rate sufficient to recirculate or turnover all of the pool water within a certain interval. For swimming pools, turnover rates of between eight and twelve hours are generally recommended. The pump size required to achieve the desired turnover rate for a particular pool depends primarily on the pool's size (e.g., gallons) and the characteristics of the plumbing system, (e.g., pipe dimensions, fittings, filter, orifices, etc). In summary, the pump must be sized to overcome the total flow resistance attributable to friction loss in the plumbing on both the suction and pressure sides of the pump. This total flow resistance is frequently referred to as “Total Dynamic Head” (TDH) and is typically expressed in “feet of water”. Many pump manufacturers provide performance data tables which indicate (for each pump size) the pump output (e.g., gallons per minute) as a function of Total Dynamic Head. An exemplary performance data table is depicted below:

TABLE I Pump Output (Gallons Per Minute) vs. Total Dynamic Head (Feet of Water) Pump HP 20 ft 30 ft 40 ft 50 ft 60 ft 70 ft ½ 55 45 29 — — — ¾ 67 58 47 31 — — 1.0 85 76 65 50 27 — 1.5 97 90 80 67 50 10 2.0 116 111 99 85 70 51 2.5 109 109 104 95 84 69

With reference to the preceding Table 1, for an exemplary pool installation characterized by a head of 40 feet where a flow rate of 47 gallons per minute is desired, a ¾ HP pump should be selected.

In addition to drawing water from the pool and returning it via a filter, many existing pool cleaning systems also utilize the pump suction (i.e., negative pressure) to power an automatic pool cleaner, typically configured for submerged travel along the surface of the pool containment wall. A typical suction powered cleaner includes an inlet for drawing in water and debris, an outlet for discharging into a flexible suction hose coupled to the pump suction inlet, and a propulsion subsystem powered by the pump suction for propelling the cleaner along the wall surface.

Conventional pool cleaning systems are typically selectively operable in either a filtering mode (in which the cleaner is deactivated and the pump suction pulls a maximum rated pool water flow from the skimmer and/or drain, hereinafter, “skimmer/drain”) and a cleaning mode (in which the pump suction is primarily used to power the cleaner). In the cleaning mode, power delivered to the cleaner functions primarily to propel the cleaner along the submerged wall surface and to vacuum debris from the wall for transport through the suction hose to the pump inlet. In typical existing systems, the water flow from the cleaner alone is frequently insufficient to satisfy pump flow requirements. Accordingly, it is typical to provide additional pool water flow to the pump inlet from the skimmer/drain to satisfy the rated pump output in order to avoid pump cavitation. Some type of flow control device, e.g., one or more valves, is generally provided between the pump suction inlet and the respective outlets of the pool cleaner and skimmer/drain for selectively defining the respective operating modes, i.e., filtering mode and cleaning mode. For example, a first flow path coupling the skimmer/drain to the pump inlet will be fully open in the filtering mode and closed or only partially open in the cleaning mode. A second flow path coupling the cleaner to the pump suction inlet will be fully open in the cleaning mode and open or closed during the filtering mode. The first and second flow paths can be controlled in a variety of ways either manually or automatically. For example, first and second valves can be respectively incorporated into the first and second flow paths and can be controlled manually or in response to a certain event such as the expiration of a timed interval or activation of the pump. Alternatively, the flow paths can be manually controlled by a user physically decoupling one flow path and coupling the other flow path to a pipe leading to the pump suction inlet.

In order to be compatible with a wide range of pool sizes employing a variety of plumbing configurations and pump sizes, commercially available pool cleaners are typically designed to be powered by a relatively low negative pressure supplied to the downstream end of the suction hose at the pool wall. More particularly, such pool cleaners are typically designed to be powered by a negative pressure of −12″ Hg or less (1.0 inch mercury equals approximately 0.88 feet water) at the pool wall. This −12″ Hg limitation is a consequence of (1) the allowable pressure drop between the pool wall and the pump suction inlet and (2) the recognition that, to avoid pump cavitation, it is advisable to maintain the pump inlet pressure less negative than −26″ Hg. The −26″ Hg limitation at the pump inlet is based on the fact that water at a temperature of 100° F. will vaporize when exposed to a vacuum of −28″ Hg and an appropriate margin of safety (i.e., about 2″ Hg) is prudent.

As an example, if a 2 H.P. pump coupled to a pool cleaner provides a negative pressure of about −12″ Hg at the pool wall, i.e., the downstream end of the suction hose, and additional pool water is supplied (i.e., from the skimmer/drain) sufficient to satisfy the rated pump output, the friction loss (e.g., about 14″ Hg) in the suction side plumbing, attributable primarily to the additional water, produces a negative pressure of about −26″ Hg at the pump inlet (i.e., −12+(−14)=−26). This pump inlet pressure is close to the cavitation point of a typical pump. If a larger pump were selected, the likelihood of cavitation increases. Similarly, if a greater negative pressure is produced at the pool wall, the likelihood of cavitation would also increase. Thus, the magnitude of negative pressure (i.e., −12″ Hg) available at the pool wall for powering the cleaner is limited and has been a barrier to the design of higher performance cleaners.

SUMMARY OF THE INVENTION

The present invention is directed to an automatic swimming pool cleaning system including a subsystem responsive to the magnitude of negative pressure at the pump suction inlet for controlling pump flow in order to prevent pump cavitation and/or create a constant high negative pressure at the pool wall for powering a pool cleaner. Systems in accordance with the invention are configured to pump a high rated volume of water when operating in a filtering mode and to provide a high negative pressure at the pool wall for powering the pool cleaner when operating in a cleaning mode. More particularly, embodiments of the invention are configured to provide a pressure at the pool wall more negative than −12″ Hg for powering a pool cleaner. This increase in available negative pressure, as contrasted with the prior art, permits the design of higher performance cleaners.

In accordance with a significant aspect of the invention, the pump flow is varied as a function of the magnitude of negative pressure at the pump inlet for the purpose of avoiding cavitation. The pump flow can be controlled in a variety of ways including mechanical, hydraulic, pneumatic, and electrical. For example, the pump can be back pressured by reducing openings at or downstream from the pump outlet to increase output flow resistance and thus avoid cavitation by reducing the flow producing capability of the pump. Alternatively, pump flow producing capability can be reduced by, for example, decreasing electric drive power to the pump motor and/or electrically and/or mechanically loading the pump to reduce pump speed.

A first subsystem in accordance with the invention for preventing cavitation includes a pressure sensor for monitoring the negative pressure at, or just upstream from, the pump suction inlet. If the monitored pressured is more negative than a lower setpoint S_(L) (e.g., −25″ Hg), the pump flow producing capability is reduced by closing a throttling valve downstream from the pump outlet to prevent the inlet pressure from falling to a level which could cause cavitation. If the monitored pressure is less negative (i.e., more positive) than an upper setpoint S_(U) (e.g., −24″ Hg), the pump flow producing capability is increased by opening the downstream throttling valve. Thus, the subsystem operates in the cleaning mode to maintain the minimum pump inlet pressure at about −25″ Hg, thus preventing cavitation.

In a preferred implementation of the first subsystem embodiment, the setpoints S_(L) and S_(U) can be set when the pump is manufactured or can be user adjustable to optimize the system for a particular pool installation. Typically, the setpoints will be adjusted when a system is initially installed and once setup, will generally not require further adjustment. The first embodiment can be implemented by using a conventional pump and locating the pressure sensor at the pump suction inlet with the flow controller (or valve device) located in the pressure side plumbing at or downstream from the pump pressure outlet. Alternatively, the pump can be manufactured with the pressure sensor and flow controller actually installed in the pump housing adjacent to the inlet and outlet, respectively.

A second subsystem in accordance with the invention includes a pressure sensor configured to monitor the negative pressure at the pool wall, e.g., at a port between a fixed pipe and the downstream end of a flexible suction hose coupled to the cleaner. In the cleaning mode, substantially all of the pump inlet flow is taken in by the cleaner with no significant flow being contributed by the skimmer/drain. The system is configured to maintain a substantially constant high negative pressure (i.e. more negative than −12″ Hg) at the wall port during the cleaning mode for powering a higher performance pool cleaner while preventing cavitation. For example, a lower setpoint S_(L) could be set to −20″ Hg and an upper setpoint S_(U) to −19″ Hg. The second embodiment can be implemented in numerous functionally equivalent ways. Preferably, a pressure sensor is physically located proximate to the wall port and configured to enable a user to manually adjust and establish the setpoints. The pressure sensor monitors the pressure at the port and communicates to a flow controller whether the measured pressure is more negative than the lower setpoint S_(L) or less negative than the upper setpoint S_(U). This communication can be by electrical means, e.g., hardwire or wireless, e.g., RF, or by hydraulic, pneumatic or mechanical means. Regardless, the flow controller is configured to respond to the pressure sensor command to modify the pump's flow producing capability, e.g., by modifying the flow resistance of the pressure side plumbing or by electrically or mechanically varying the pumping capacity of the pump.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 diagrammatically depicts a prior art pool cleaning system including a pump for drawing in pool water from a skimmer and returning the water to the pool via a filter, the system further including a traveling pool cleaner powered by pump suction;

FIG. 2 is a block/flow diagram of the prior art system of FIG. 1;

FIG. 3 depicts performance curves for an exemplary pool cleaner and exemplary ¾ and 2.0 HP pumps operating in accordance with a typical prior art system as shown in FIG. 2 and a system in accordance with the invention as shown in FIGS. 4A and 5;

FIG. 4A is a diagram similar to FIG. 2 but modified to show improvements in accordance with the invention for preventing pump cavitation;

FIG. 4B is a schematic diagram showing a pressure sensor and valve for controlling pump back pressure; and

FIG. 5 is a diagram similar to FIG. 4A configured to establish and maintain a desired negative pressure at the downstream end of the cleaner suction hose.

DETAILED DESCRIPTION

Attention is initially directed to FIG. 1 which diagrammatically depicts an exemplary conventional system for cleaning the water in pool 20 (i.e., filtering mode) as well as cleaning the surface of wall 22 (including bottom and side portions) containing the pool (i.e., cleaning mode). Water cleaning, i.e., filtering, is accomplished primarily by causing pump 24 to pull pool water 20 through skimmer and or drain 26 (“skimmer/drain”) through suction side plumbing 28 to the pump suction inlet 30. The pump pressure outlet 32 returns the water to the pool via a filter 34, and optionally a heater 36 and/or chlorinater via pressure side plumbing 38 to one or more return outlets 40.

Wall cleaning is primarily achieved by operating an automatic traveling pool cleaner 44 which is coupled via a flexible suction hose 46 and plumbing 28 to the pump suction inlet 30. The suction, i.e., negative pressure, provided by the pump 24 to the cleaner 44, powers the cleaner primarily to (1) propel it along the surface of wall 22 and (2) pull pool water from adjacent the wall surface 22 for passage along with water borne debris, via suction hose 46 and plumbing 28 to pump suction inlet 30. The pool water drawn from the skimmer 26, as well as the pool water drawn from cleaner 44 through suction hose 46 and standpipe 47, passes through an accessible skimmer basket 50 for trapping large debris prior to it reaching the pump 24.

The typical system shown in FIG. 1 includes a valve 52, mounted in shimmer vacuum plate 53, which operates alternately in a pool water filtering mode and a cleaning mode. In the filtering mode, valve 52 is fully open so that the pump maximum rated flow can be pulled from the skimmer/drain for passage through the filter. In the cleaning mode, valve 52 is typically partially open to an adjustable setpoint so that pool water can be pulled from the cleaner 44 to operate the cleaner.

The valve 52 can be controlled manually and/or automatically to operate in the cleaning mode for a certain interval, e.g., 3-4 hours per day. A longer interval, e.g., 8-12 hours per day is typically required in the filtering mode to draw all of the pool water from the skimmer/drain for passage through filter 34. A master timer (not shown) is generally provided to define these respective cleaning and filtering intervals.

Attention is now directed to FIG. 2 which illustrates the exemplary system of FIG. 1 in greater functional detail. FIG. 2 depicts a conventional pump 100 having a suction inlet 102 and a pressure outlet 104. The pump 100 is comprised of an electrically driven motor and an impeller which is configured so that when rotated, it is capable of drawing water into the inlet 102 and discharging water at the outlet 104. This action produces a negative pressure or suction at 102 and a positive pressure at 104. The outlet 104 is coupled through pressure side plumbing 106 typically including return line 108 extending to return outlets 110, preferably adjustable “eye-ball” flow director(s) mounted on the pool wall, for returning water to the pool. The pressure side plumbing 106 includes a filter 112 and, optionally, equipment such as a heater 114, a chlorinater, etc. FIG. 2 also depicts a skimmer 120 having a pool water inlet 124 and a pool water outlet 126. Typical prior art pool cleaning systems also include a drain 128 defining a pool water inlet 130 and outlet 132. The skimmer and drain outlets 126, 132 are typically joined together at junction 136 upstream from the pump suction inlet 102.

FIG. 2 depicts the junction 136 as being coupled to inlet port 138 of valve V1 140 (corresponding to aforementioned valve 52) whose outlet port 142 is coupled via pipe length 144 to the pump suction inlet 102.

FIG. 2 also depicts a traveling pool cleaner 146 having a pool water inlet 148 and outlet 150. The outlet 150 is coupled to the upstream end 151 of a flexible suction hose 152. The hose downstream end 153 is typically coupled to a suction side plumbing port 154 (e.g., the inlet to standpipe 47 in FIG. 1) located proximate to the pool wall 156. FIG. 2 depicts the port 154 as being coupled through a valve V2 158 and pipe or conduit 144 to the pump inlet 102.

It is important to note that the valves (V1, V2) 140 and 158 depicted in the exemplary prior art system of FIG. 2 are not intended to necessarily represent identifiable hardware valves. Rather, the depicted valves 140 and 158 are intended to broadly represent any functional means for affecting flow between (1) the junction 136 and pump inlet 102 and (2) the hose end 153 and pump inlet 102. Whereas some prior art systems may actually use conventional manual or timer controlled valves, other systems may rely upon a user physically coupling or decoupling respective openings, e.g., the hose end 153 and port 154.

Regardless of the specific implementation, FIG. 2 is intended to functionally represent how the flows are controlled for operation in respective filtering and cleaning modes. In the filtering mode, the flows are controlled to move pool water at a maximum rate through pump 100 and filter 112. In the cleaning mode, the flows are controlled to apply adequate suction to hose end 153 for powering the cleaner 146. The flow control chart shown in FIG. 2 depicts the functioning of the depicted valves V1, V2 when operating in the filtering and cleaning modes. In the filtering mode, valve V1 is fully open for carrying the maximum rated flow to the pump and filter. V2 can be open or closed. In the cleaning mode, valve V2 is fully open and V1 is typically at a setpoint for supplying adequate additional pool water flow to pump 100 to avoid cavitation.

Typical swimming pool installations employ a pump sized to fully recirculate the pool water in about 8-12 hours. The pump size selected for any particular pool installation is determined primarily by the pool's capacity and the total friction loss attributable to both the suction side plumbing, i.e., upstream from suction inlet 102, and the pressure side plumbing, i.e., downstream from pressure outlet 104. This total resistance is generally referred to as total dynamic head and is typically measured in feet of water. A proper pump size can be selected for a particular pool installation by knowing the total dynamic head and the pool capacity. Based on these input quantities, a desired flow rate in gallons per minute can be determined. This flow rate for a particular head determines the pump size which should be selected. The exemplary performance data Table I set forth above shows, for example, that to achieve a 47 gallon per minute flow rate with a 40 foot head, a ¾ HP pump should be selected. The table depicts flow rates for pumps sized from ½ HP to 2.5 HP which represents the typical range of pump sizes used in normal residential swimming pool installations.

Various suction powered pool cleaner constructions are commercially available and described in the literature. In order to be compatible with a full range of pool pump sizes, these known pool cleaners have typically been designed to be powered by a relatively small negative pressure, e.g., −12″ Hg or less, available at the downstream end 153 of hose 152, i.e., at the pool wall. It is generally thought that a greater negative pressure cannot be made available at the wall because of the likelihood of causing pump cavitation. Inasmuch as water at a temperature of 100° F. exposed to a vacuum of −28″ Hg can boil and cause pump cavitation, it is generally considered prudent to maintain a safety margin and prevent the pump inlet pressure, i.e., at 102, from being more negative than about −26″ Hg. In order to satisfy normal pump flow requirements, the skimmer/drain must typically supply sufficient additional pool water via valve V1 140. This additional flow can produce a significant friction loss in pipe 144. For example, when using a 2 HP pump, the pressure drop through the pipe 144 could be on the order of 14″ Hg. Consequently, the negative pressure of −26″ Hg available at the pump suction inlet 102 would be reduced by the 14″ Hg loss in the pipe 144 leaving only a negative pressure of −12″ Hg at the downstream end 153 of suction hose 152 for powering the cleaner 146. The negative pressure actually available to the cleaner is even further reduced by the pressure loss in hose 150. Accordingly, in view of the foregoing, it has typically been the practice to design the pool cleaner 146 such that it can be powered by a negative operating pressure of −12″ Hg or less at the wall. This relatively low negative pressure design parameter presents a significant barrier to the design of higher performance pool cleaners.

FIG. 3 charts negative pressure at the wall port in inches of mercury (vertical axis) vs. pool water flow rate in GPM (horizontal axis) for an exemplary pool cleaner and typical ¾ and 2 HP pumps which can be used with the cleaner. The pump curves assume that the output flows into a clean filter. The fact that the cleaner performance curve 160 fails to intersect either pump performance curve 162, 164 demonstrates the conventional need in the cleaning mode to provide additional pool water flow from the skimmer/drain to satisfy the pump flow requirements to prevent cavitation. For example, at a wall port pressure of −12″ Hg, the horizontal distance AB represents the additional pool water flow required from the skimmer/drain to prevent cavitation when the cleaner is operating with the ¾ HP pump. Similarly, the distance AC represents the additional pool water flow required when the cleaner is operating with the 2 HP pump.

The additional pool water flow provided via the skimmer/drain produces a pressure drop between the wall port 154 and the pump inlet 102 (FIG. 2). Inasmuch as it is important to prevent the negative pressure at the pump inlet from becoming more negative than −26″ Hg to avoid cavitation, the pressure drop attributable to large pump flow requirements restricts the magnitude of negative pressure which can be provided at the wall port for powering the cleaner. The foregoing demonstrates why prior art cleaners are generally designed to operate with relatively small wall port pressures, e.g., −12″ Hg or less.

In accordance with the present invention, instead of supplying additional pool water from the skimmer/drain to satisfy pump flow requirements, the pump flow capability is modified to effectively shift the pump performance curves (i.e., 162 or 164) to the left, i.e., curve position 166, relative to the cleaner curve 160, as depicted in FIG. 3. This action reduces or eliminates the need to pull additional water from the skimmer/drain during the cleaning mode and permits a more negative wall port pressure to be attained without causing cavitation. More particularly, note that the cleaner curve 160 intersects the modified pump curve 166 at a wall port pressure of approximately −20″ Hg meaning that no additional pool water need be supplied from the skimmer/drain to satisfy the pump flow requirement.

The present invention is primarily directed to modifications of the plumbing configuration represented in FIG. 2 for the purposes of preventing pump cavitation and increasing the magnitude of negative pressure available at the wall port for powering the pool cleaner 146.

FIG. 4A shows a first subsystem embodiment indicating how the system of FIG. 2 can be modified, either at the pump manufacturing stage or by modifying the suction side and pressure side plumbing of a pool installation, for avoiding pump cavitation. FIG. 5 shows a second exemplary subsystem embodiment for establishing and maintaining a pressure more negative than −12″ Hg at the wall port for powering the cleaner and avoiding cavitation during the cleaning mode.

Attention is now directed to FIG. 4A which depicts the modifications to FIG. 2 for the purpose of controlling the pump flow requirements for the purpose of avoiding pump cavitation. More particularly, in accordance with the invention, a pressure sensor 200 is provided for sensing the negative pressure at the pump suction inlet 102 (which should be understood to include sites upstream therefrom). The pressure sensor 200 defines an adjustable setpoint S (or preferably a setpoint range defined by an upper setpoint S_(U) and lower setpoint S_(L)). The pressure sensor responds to a sensed pressure more negative than S_(L) or less negative than S_(U) to provide a command signal to flow controller 202. The flow controller 202 functions to modify the flow requirements of pump 100 for the purpose of maintaining the pump inlet pressure at a level to avoid cavitation, i.e., at about −25″ Hg.

In accordance with the invention, the flow controller 202 can be implemented in a variety of ways (e.g., electronic, hydraulic, pneumatic, mechanical) for controlling the pump flow requirements. For example, flow controller 202 can control, via link 206, a variable throttling valve V3 210 located at the pressure outlet 104 (which should be understood to include sites downstream therefrom). Alternatively, the controller 202 can vary the pumping capacity of pump 100 by controlling pump motor speed via motor control circuit 212 or by mechanical loading, e.g., via a brake (not shown).

It is pointed out that communication between the pressure sensor 200, flow controller 202, and throttling valve V3 210 can also be implemented in a variety of ways, e.g., by a hydraulic, pneumatic, or mechanical link or electrically via hardwire or wirelessly.

Attention is now directed to FIG. 4B which illustrates an exemplary embodiment of pressure sensor 200 in conjunction with flow controller 202 and throttling valve 210 of FIG. 4A. The pressure sensor 200 is comprised of an extendible cylindrical wall or bellows 220 closed by upper and lower plates 221, 222 to define an interior chamber 224. Chamber 224 opens via port 226 in plate 222 and port 227 in pump inlet pipe 228 to the pressure at pump inlet 102. Thus, a relative increase in pump inlet pressure will tend to move upper plate 221 away from lower plate 222 and a relative decrease in pump inlet pressure will tend to pull plate 221 closer to plate 222.

Plate 221 carries a rod 230 extending through an opening 231 in fixed plate 232. The upper end of rod 230 is threaded at 233 and threadedly coupled to an adjustable nut 234. A coil spring 235 is accommodated between nut 234 and fixed plate 232. The spring 235 acts against nut 234 to urge the rod 230 upwardly (as viewed in FIG. 4B) to expand the chamber 224. A relative decrease in pump inlet pressure acts to pull plate 221 down against the tension of spring 235 which is determined by the adjustable position of nut 234.

Rod 230 carries a switch actuator 236 which cooperates with normally open motor switches 238, 239. The switches are mounted such that actuator 236 closes switch 238 when rod 230 moves to the upper end of its range and closes switch 239 when rod 230 moves to the lower end of its range.

Switch 238 is connected to valve motor 240 to rotate valve V3 toward a fully open position when switch 238 is closed. FIG. 4B depicts switch 238 as being connected in series with an electric power source 242 and a normally closed limit switch 243 to a drive terminal 244 of valve motor 240. Energization of terminal 244 rotates valve V3 toward an open position. When valve V3 reaches its fully open position, limit switch 243 opens to deenergize motor 240.

Switch 239 is similarly connected to valve motor 240 to rotate valve V3 toward a closed position when switch 239 is closed. Switch 239 is connected in series with power source 242 and a normally closed limit switch 245 to drive terminal 246 of valve motor 240. When valve V3 rotates to its closed position, limit switch 245 is opened to deenergize motor 240.

From the foregoing, explanation of FIGS. 4A, 4B it should now be understood that valve V3 can be rotated within a range from fully open to closed as determined by the pressure sensed at port 227 proximate to the pump inlet 102. The sensed pressure establishes the dynamic position of plate 221 and switch actuator 236 to control motor switches 238, 239 and thus the state of valve V3.

In normal operation, if the sensed pressure becomes too negative, i.e., more negative than S_(L), plate 221 will be drawn down to rotate valve V3 toward the closed position. On the other hand, if the sensed pressure becomes too positive, i.e., less negative than S_(U), plate 221 will be moved upward to close switch 238 to rotate valve V3 toward its open position. In this manner, the pressure at the pump inlet 102 can be dynamically adjusted to maintain it close to −25″ Hg to prevent pump cavitation.

Attention is now directed to FIG. 5 which depicts alternative modifications to FIG. 2 for the purpose of controlling the pump flow requirements when operating in the cleaning mode in order to maintain an increased negative pressure, i.e., more negative than −12″ Hg at the pool wall port 153 for operating the suction cleaner 146. More particularly, in accordance with the invention, adjustable pressure sensor 300 is initially adjusted to set the wall port pressure at a desired level, e.g., −20″ Hg. The sensor 300, which can be similar to sensor 200 depicted in FIG. 4B, functions to generate a command to flow controller 302 for controlling throttling valve 310 and/or motor control circuit 312. Communication can be accomplished by any suitable means such as a pneumatic, hydraulic, or mechanical link, or via a wired or wireless electrical connection. By controlling the action of valve 310 and/or control circuit 312, the pump curve, e.g., 162 or 164, in FIG. 3 is shifted left to curve position 166, thus enabling the system to operate in the cleaning mode without requiring significant additional water flow from the skimmer/drain for preventing cavitation. As a consequence, a significant pressure drop between the wall port 153 and the pump inlet 102 is avoided and a higher constant pressure more negative than −12″ Hg, e.g., −20″ Hg is available at the wall port for powering cleaner 146. The availability of a higher negative pressure enables higher performance cleaners to be used.

It is pointed out that the sensor 300 and flow controller 302 will function to maintain the desired pressure at the wall port despite the occurrence of events such as a partial occlusion in the pressure side plumbing, e.g., the filter becoming dirty. Such an event can be viewed as merely shifting left the clean filter pump curves depicted in FIG. 3.

The foregoing description of FIG. 5 discusses the operation in the cleaning mode. In the filtering mode, the flow controller 302 fully opens valve V3 enabling the pump to draw the rated flow for filtration from the skimmer/drain. Thus, a system in accordance with the invention as depicted in FIG. 5 operates to enable the pump to produce its rated flow in the filtering mode and produce a higher negative pressure for operating the cleaner 146 in the cleaning mode without causing cavitation.

From the foregoing, it should now be appreciated that a method and apparatus has been described for controlling a swimming pool pump so as to produce an increased negative pressure for driving a pool cleaner while assuring sufficient water flow to avoid pump cavitation. Although only two exemplary embodiments have been specifically described, it should be recognized that variations and modifications will occur to those skilled in the art coming within the spirit and intended scope of the appended claims. 

1. A method of operating a pool cleaning system comprised of a water pump, suction side plumbing coupling a pool water inlet to a suction inlet of said pump, and pressure side plumbing coupling a pressure outlet of said pump through a filter to a pool water return outlet, said method comprising: sensing the pressure at a site at the suction side of said pump; and responding to said sensed pressure for controlling water flow from said pump outlet.
 2. The method of claim 1 further including: setting a setpoint for pressure at said site; and responding to a sensed pressure more negative then said setpoint for reducing water flow from said pump outlet.
 3. The method of claim 1 further including: setting a setpoint for pressure at said site; and responding to a sensed pressure more positive then said setpoint for increasing water flow from said pump outlet.
 4. In a system for cleaning a water pool including: a pump having a suction inlet and a pressure outlet; pressure side plumbing including a filter coupling said pressure outlet to at least one pool return outlet; means defining a pool water inlet; a pool cleaner configured to be powered by suction for traveling through said water pool; and suction side plumbing including a first flow path coupling said pump suction inlet to said pool water inlet and a second flow path coupling said pump suction inlet to said pool cleaner; the improvement comprising: a flow controller responsive to the pressure at the suction side of said pump for controlling output flow from said pump to prevent pump cavitation.
 5. The system of claim 4 further including: a pressure sensor for monitoring pressure at a site at the suction side of said pump; and wherein said flow controller is responsive to said monitored pressure being more negative than a setpoint for reducing the output flow from said pump.
 6. The system of claim 5 wherein said flow controller operates to reduce said output flow by increasing the flow resistance at the pressure side of said pump.
 7. The system of claim 5 wherein said flow controller operates to reduce said output flow by reducing the pumping capacity of said pump.
 8. The system of claim 4 further including: a pressure sensor for monitoring pressure at a site at the suction side of said pump; and wherein said flow controller is responsive to said monitored pressure being more positive than a setpoint for increasing the output flow from said pump.
 9. Apparatus for cleaning a water pool comprising: a pump having a suction inlet and a pressure outlet; a skimmer/drain defining a pool water inlet and a pool water outlet coupled to said pump suction inlet; a pool cleaner defining a pool water inlet and a pool water outlet coupled to said pump suction inlet; and control means responsive to the pressure at the suction side of said pump for controlling water flow from said pressure outlet, said control means including: a sensor for sensing the pressure at the suction side of said pump; and a flow controller responsive to said sensed pressure for controlling water flow from said pump pressure outlet to maintain said sensed pressure at a predetermined level.
 10. The apparatus of claim 9 wherein said pump includes a motor and said control means includes a motor control circuit connected to said motor; and wherein said flow controller is coupled to said motor control circuit for controlling the pumping capacity of said pump.
 11. In a system for cleaning a water pool contained by a wall including: a pump having a suction inlet and a pressure outlet; pressure side plumbing including a filter coupling said pressure outlet to at least one pool return outlet; a skimmer/drain defining a pool water inlet; a pool cleaner defining a pool water inlet and configured to be powered by suction for traveling through said water pool; and suction side plumbing including a first flow path coupling said pump suction inlet to said skimmer/drain pool water inlet and a second flow path coupling said pump suction inlet to said pool cleaner, said second flow path including a conduit extending from said suction inlet to a port in said wall and a suction hose coupling said port to said cleaner; the improvement comprising: a pressure sensor for monitoring the pressure proximate to said wall port; and a flow controller responsive to said monitored pressure for controlling water flow from said pump outlet for producing a substantially constant pressure more negative than −12″ Hg at said wall port for powering said cleaner.
 12. The system of claim 11 including means for adjustably establishing a pressure setpoint; and wherein said flow controller is responsive to said monitored pressure being more negative than said setpoint for reducing the output flow from said pump.
 13. The system of claim 12 wherein said flow controller operates to reduce said output flow by increasing the flow resistance at said pressure outlet.
 14. The system of claim 12 wherein said flow controller operates to reduce said output flow by reducing the pumping capacity of said pump.
 15. The system of claim 11 including means for adjustably establishing a pressure setpoint; and wherein said flow controller is responsive to said monitored pressure being more positive than said setpoint for increasing the output flow from said pump.
 16. The system of claim 15 wherein said flow controller operates to increase said output flow by reducing the flow resistance at said pressure outlet.
 17. The system of claim 15 wherein said flow controller operates to increase said output flow by increasing the pumping capacity of said pump. 